UCSC study: Energy production causing quakes

SANTA CRUZ -- A new UC Santa Cruz study concludes that a CalEnergy geothermal field near the Salton Sea is triggering small earthquakes very close to the San Andreas Fault, a finding with potentially big implications.

Published Thursday in the journal Science, the study draws a straight line between pulling water out of the ground and increasing numbers of temblors. The conclusion is sure to add to a growing debate about whether a new generation of energy production methods -- even those aimed at renewable sources -- could have unintended effects with potentially serious consequences.

"We're not the first people to ever say that pulling fluid out of the ground is causing earthquakes, but the demonstration here is much clearer," said the study's chief author, UCSC geophysicist Emily Brodsky. "It's a very strong signal. This is not subtle."

The study examined more than 30 years of data from CalEnergy production facilities near Brawley, but could have broader implications. Tinkering with subterranean pressure dynamics is a staple of modern oil and gas production, and if they cause earthquakes it could prove a sensitive topic in California, where lawmakers are grappling with new regulations for the emerging technologies.

At CalEnergy's Imperial Valley operation, the company taps into naturally heated deep-water reservoirs located thousands of feet below the surface. That water is then flash-steamed to help produce geothermal energy before being pumped back into the ground.

But some of the water is lost during the process, which is one source of the problem. CalEnergy's facilities are in a seismically active area, and the vast majority of the earthquakes are not large enough to pose a threat to human life or property.

"There are many more little earthquakes in this world than big earthquakes, and this is no exception," said Brodsky, though she added her data included a 5.1-magnitude quake, and that the risk of triggering a large one was more than zero.

A CalEnergy representative declined to comment. The San Andreas Fault ends across the Salton Sea from CalEnergy's facilities, and the Imperial Fault is also nearby. CalEnergy is a subsidiary of MidAmerican Energy Holdings, which is controlled by Berkshire Hathaway.

Scientists at Lawrence Berkeley National Laboratory said "induced seismicity" is an accepted phenomenon within the scientific community. As far back as the 1930s, oilmen around Long Beach noticed they needed to replace oil with saltwater or the ground would shake, said Ernest Majer, a senior adviser in the lab's geophysics department.

"Reinjecting water and taking water out of the ground has been long known to cause seismicity," said Majer, an authority on the topic.

The phenomenon is only new to the general public, said his colleague, Stefan Finsterle, a hydrogeologist.

"It just boiled to the top of the public's perception in recent years because of fracking," Finsterle said.

FRACKING CONCERNS

Fracking is a technique that taps previously unrecoverable oil resources. But it is a water-intensive process, and federal officials and advocacy groups are concerned about the disposal water, which contains chemicals and is often injected back into the ground.

In a state riven with fault lines and vast, untapped oil potential -- particularly beneath the Monterey Shale, a geologic formation that expands east into the Central Valley from Monterey County -- there has been surprisingly little debate about the earthquake risks from fracking. There are 88,000 active wells in California, helping make the state the fourth-largest oil producer in the U.S. California also tops the nation in geothermal production.

This year, various state lawmakers proposed a series of fracking-related bills, but just one survives. It now includes the remnants of a bill proposed by Assemblyman Mark Stone, D-Scotts Valley, establishing standards governing fracking wastewater.

But that onmibus bill does not address seismic concerns. Stone said the link is "seen as a myth" in Sacramento, adding that the state needs to take a harder look at the issue.

"If they're potentially causing earthquakes in areas that don't have earthquakes" such as the Midwest, Stone said, "what's going to happen in areas that are susceptible to earthquakes?"

QUAKES STUDIED

Last year, the U.S. Geological Survey concluded that a new prevalence of Midwest earthquakes had to be manmade -- with a sixfold increase over the previous century -- but stopped short of saying what human activity was causing the earthquakes.

A 2012 University of Texas study cited fracking for a series of small earthquakes around the Barnett Shale in North Texas. And in March, scientists published a study blaming a 2011 5.6-magnitude Oklahoma quake on fracking, saying a relatively small wastewater injection triggered a cascade of small earthquakes that became a larger one.

Jason Marshall, chief deputy director for the California Department of Conservation, said more than a million fracking wells have been drilled nationally without evidence they cause earthquakes. The state recently studied available data from California wells and found they are drilled to an average of nearly 3,000 feet and use an average of 143,000 gallons of water, which is much less than in other states.

But it is the associated process of reinjecting wastewater into the ground that has been the focus of seismic studies. Marshall said the state has "Underground Injection Control" regulations keeping oil producers from increasing underground water pressure beyond normal circumstances, which have kept induced earthquakes from becoming an issue here.

Majer said some changes are on the horizon after a recent court ruling over fracking on federal lands. There, a San Jose federal magistrate said the Bureau of Land Management must update its oversight of fracking wells, a process Majer said could include a look at seismic regulations.